1. Field of the Invention
One embodiment of the present invention relates to a secondary battery.
Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. In addition, one embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, a power storage device, a storage device, a method for driving any of them, and a method for manufacturing any of them.
2. Description of the Related Art
In recent years, a variety of power storage devices, for example, secondary batteries such as lithium-ion secondary batteries, lithium-ion capacitors, air batteries, and fuel batteries have been actively developed (Patent Documents 1 to 4). In particular, with the development of the semiconductor industry and with the growing demand for energy saving, the uses of lithium-ion secondary batteries with high output and high energy density have rapidly expand to include, for example, portable information terminals such as cellular phones, smartphones, and laptop personal computers; electric devices such as portable music players and digital cameras; medical equipment; next-generation clean energy vehicles such as hybrid electric vehicles (HEVs), electric vehicles (EVs), and plug-in hybrid electric vehicles (PHEVs); stationary power storage devices; and the like. The lithium-ion secondary batteries are essential for today's information society. Furthermore, with the growing expectations for flexible devices or wearable devices in recent years, development of lithium-ion secondary batteries that have flexibility to be deformed following deformation of devices, i.e., flexible lithium-ion secondary batteries is urgently necessary.
A lithium-ion secondary battery, which is a nonaqueous secondary battery, includes a positive electrode, a negative electrode, a separator, a nonaqueous electrolyte solution, and an exterior body covering these components. In lithium-ion secondary batteries, positive electrodes and negative electrodes are generally used; the positive electrodes each include a positive electrode current collector made of aluminum or the like and a positive electrode mix which includes a positive electrode active material capable of occluding and releasing lithium ions and which is applied to each surface of the positive electrode current collector, and the negative electrodes each include a negative electrode current collector made of copper or the like and a negative electrode mix which includes a negative electrode active material capable of occluding and releasing lithium ions and which is applied to each surface of the negative electrode current collector. These positive and negative electrodes are insulated from each other by a separator provided therebetween, and the positive electrode and the negative electrode are electrically connected to a positive electrode terminal and a negative electrode terminal, respectively, which are provided on the exterior body. The exterior body has a certain shape such as a cylindrical shape or a rectangular shape.